Animals have the ability to adapt to many and varied environmental conditions. The limit of adaptation depends mainly on the animal's absolute physiological limitations and the rate of environmental change or adaptive pressure to which it is subjected.
Perhaps the most difficult transition a mammal is required to make in its lifetime is the change from the intruaterine environment to the extrauterine environment at birth. Every parameter of the infant's environment changes abruptly. Dramatic shifts in temperature, tactile sensation, audio stimuli, motion and light are exacerbated by conditions in the hospital delivery room where most women in modern societies give birth. Even the environment in a loving home is alarmingly unfamiliar, and many infants exhibit prolonged trying and sleeplessness which may be related to transitional stress. It is believed that these abrupt changes in the environment tend to intensify the infant's intrauterine to extrauterine transition and may inflict harm which affects the person's emotional and physical response to adaptive or environmental change throughout the remainder of his or her life. Therefore a gradual and effective transition of the infant from the intrauterine environment to the extrauterine environment may have substantial long-term as well as short-term benefits.
Additionally, an infant may encounter medical situations which involve tubes and needles entering and exiting its body, or situations where a surgical procedure is necessary. In such cases, there is not only a strong desire to minimize the infant's stress level, but a need to physically stabilize the infant. The stabilization minimizes opportunity for injury and also assists medical personnel performing surgical procedures. Traditional infant housings do not adequately address these dual requirements of comfort and stabilization.
An effective transition system would duplicate as closely as conveniently possible the intrauterine conditions perceived by the infant just prior to birth. It would also provide means for gradually altering environmental stimuli over time until they reflected the natural extrauterine environment.
The environmental stimuli vary in complexity and ease of simulation or control. Light and temperatures are relatively easy to simulate and vary. The sound parameter, while complex in nature, may be generated and controlled by standard means. The motion parameter, however, is quite distinctive. FIG.1 shows the characteristic pelvic displacement patterns of pregnant women while walking. Duplicating the linear and rotational components of these motions is difficult and requires a sophisticated suspension and motion control and drive system.
U.S. Pat. No. 4,079,728 discloses a programmable environmental transition system with means to provide and control two or more of the above-mentioned environmemtal stimuli and to modify them over time from initial values closely approximating what the fetus perceives in the uterus just prior to birth to final values typical of the extrauterine environment. Rather than duplicate any particular motion pattern, the system imparts a general rocking motion to the infant, who is suspended therein on a net-like sling.